Electrical wave signaling system



Aug 29, 1950 E. H. uLLRlcH 2,520,184

ELECTRICAL WAVE SIGNALING SYSTEM original Filed Nov.` 8, 1941 900` /aooY 27oo 36d@ F/GZ.

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Patented ug. 29, ,195

ATENT oFEicE n 2,520,184 ELECTRICAL WAVE SIGNALING SYSTEM Edward HillUllrich, London, England, assigner. by mesne assignments,l 'toInternational Standard Electric Corporation, corporation of Delaware NewYork, N. Y., a

`Original application November 8, 1941, Serial No.

418,281, 7, 1945. Divided and 'th 1945, Serial No. y602,45 1940 1 Claim.(Cl. Z50-6) The present invention relates to electric wave signallingsystems comprising a plurality of transmitters widely spaced so as to bereceived at a, receiving station from diiferent directions. This is adivision of U. S. application Serial No. 418,281 Aledj November 8, 1941which has since issued into U. S. Patent No 2,381,847 on August 7, 1945.

The transmitting stations may be radiating on the same wave lengths oron wave lengths which are slightly different from each other, andincludes the case in which at a receiver interference is causedpurposely in the transmission from one of the transmitters by thetransmission from another transmitter, the two transmitters beingseparated by some distance.

In such a network of radio transmitting stations the fading produced ata receiver will generally be diiferent for the radiations received fromthea different transmitting stations which will be located in differentdirections with respect to the receiver.

It is an object of this invention to provide means for increasing theapparent directivity and eiciency of an antenna so oriented that thereceiver receives only the desired intelligence wave.

The invention `will be exemplied in connection with impulse modulatedtransmission and with a directional frame antenna at the receiver but itwill be :understood by those skilled in the art that the invention isapplicable to any kind of transmission and any kind of directionalantenna at the receiver. For the sake of simplicity it will be assumedthat the receiver has a passband of innite width. A receiver accordingto the invention ,comprises a non-directional antenna and a directionalantenna such as a frame aerial, each connected respectively to alimiting amplifier. After rectification, the outputs of these amplifierscontain all the pulses except those which come from a direction in whichthe frame aerial has zero reception. Since the amplifiers containlimiting arrangements, all the pulses will have amplitudes of the samevalue. The two amplifier detectors are connected in opposition. Thus,only those pulses remain which arrive in the direction of zero receptionof the frame aerial. If the pulse is stronger by 6 decibels (db.) thanthe interference, then the corresponding output will be free frominterference.

The invention will now be described in relation to the accompanyingdrawings in which:

Figure 1 illustrates the directional diagrams of a frame and of anon-directional antenna; and

now Patent No..2,381,847, dated August is application June 30,- 3. InFrance April 4,

Figure 2 represents schematically partially in block schematic, a systemaccording to the invention incorporating a receiver for highly directivereception of a pulse-modulated signal wave.

If signals of the same intensity are received from all directions, thenin the output of the frame antenna, the strength of these signals willvary as a function of the angle of the plane of inci-dence of the wavesalong curve I, the in- :tensity of the signals being indicated along theordinates and the inclination along the abscissa.A The strength of thesignals in the output of the non-directional antenna is represented by astraight line 2. If, in each case the limiter reduces the intensity ofthese signals to the value represented by the ordinate 3 then the onlysignals resulting from connecting the outputs of the two amplifiers inopposition will be those which are included within the angles, such as 4and 5 in the Figure 1.

It should be noted that the phase of the highfrequency signal leavingthe frame antenna changes by at the points 6 and 1. If, therefore, thedetectors following the amplifiers were eliminated, then the output ofthe limiting amplii-ler of the frame could be connected in oppositionbetween zero and the point 6 with that of the limiting amplifier of thenon-directional antenna, but the two output will be additive betweenpoints 6 and This disadvantage may be eliminated, e. g. by means of thecircuit of the receiver shown in Fig. 2.

In this figure the differently located transmitters are represented bythe blocks 8a, 8b, 8c, there being any desired number. The frame ordirectional aerial is represented at 9 with the non-directional antennaat III. The antennae 9 and I0 are connected, respectively, to theamplifiers II and I2 connected in turn to the limiting devices I3 and Ithrough arrangements I5 and |16 which produce outputs independent of thesign of the input Wave. Such arrangements may be in the form of twofrequency-doubling devices of any well-known type. The outputs of thelimiting devices, I3 and I 4, are-connected to a differentialtransformer il which feeds a receiver I8 adapted to the reception ofpulse modulation. Since the arrangements I3 and I4 double the frequency,the receiver I8 must have a corresponding band width.

It will be seen that any directional antenna may be used since the phaseof the signal received by any directional antenna changes by 180 inpassing through a direction of zero reception.

n order to avoid the production of undesired frequencies by the limiter,it is necessary in principle that all transmitting stations have thesame frequency. If avrelativel'y strong wave having frequency F and aweaker waveY having a frequency f, be applied to a limiter, then in theoutput of the limiter, not only these two frequencies will be found butalso the freque ncyF-f, i. e. the image frequency of the weak Wave withrespect to the strong wave. Since the intensity of a wave in the outputof an antenna `depends on the directivity of the latter, it is` possiblethat the stronger wave be different in the outputs of the two antennae.However, this will cause only rarely any disturbance because theimpulses are very short and only one signal is present at a time. Theinvention can, therefore, be usefully applied even where the frequenciesof the received messages are different.

Although the invention has been explained as applied to waves modulatedby impulses, it need not be limited to such systems, plied tofrequency-modulation systems also. In fact, although the imagefrequencies are not the same in the output of the limiters, it ispossible to arrange that the waves of undesired stations are inopposition and to suppress the disturbance by certain image frequenciesbeing less confusing than disturbance by undesired stations.

Y It will be understood that the invention is not limited to theembodiments herein disclosed but may be modified in many ways withoutdeparting from the spirit thereof.

What is claimed is:

A receiving arrangement for receiving energy but may be apa52o,184 ff y4 waves from a plurality of different directions conprising anon-directional antenna and a directional antenna, translating meanseonnected to each of said antennas each comprising a wave frequencydoubler circuit and a, limiter connected to the output of said doublercircuit, means for combining the outputs of said limiters in phaseopposition and detecting means connected to the output of `saidcombining means.

EDWARD HILL ULLRICH.

REFERENCES CITED The following references are of record in the file ofthis patent:

Y UNITED vSTATES PATENTS Number Name Date 1,468,049 Taylor Sept. 18,1923 1,702,440 Hinton Feb. 19, 1929 1,839,290 Bailey Jan. 5, 19322,104,635 Breedlove Jan. 4, 1938 2,107,633 I-Iooven Feb. 8, 19382,216,517 Oosterhuis Oct. 1, 1940 2,226,836 Sinninger Dec. 21, 19402,238,951 YSmith et al Apr. 22, 1941 2,279,466 Johnske et al. Apr. 14,1942 2,320,908 Busignies June 1, 1943 2,350,702 Ullrich June 6, 19442,396,884 Robinson Mar. 19, 1946 2,406,799 Busignies Sept. 3, 1946FOREIGN PATENTS Number Country Date 621,731 France Nov. 8, 1929 720,624France Dec. 4, 1931

